Programming Notes

[JS] When upgrade Webpack from v3 to v4…

When I upgraded Webpack from v3 to v4, I got a bunch of errors. I already get used to encountering the errors when I upgrade the Webpack, sigh…😩

The first 2 errors I encountered were CommonsChunkPlugin and UglifyJsPlugin.

Error: webpack.optimize.CommonsChunkPlugin has been removed, please use config.optimization.splitChunks instead.
...
Error: webpack.optimize.UglifyJsPlugin has been removed, please use config.optimization.minimize instead.

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[Ubuntu] Install Hadoop 3.0.0 & Hive on Ubuntu 16.04

What’s Hadoop?

Hadoop is an open-source framework that allows to store and process big data in a distributed environment across clusters of computers using simple programming models. It is designed to scale up from single servers to thousands of machines, each offering local computation and storage.

The project includes these modules:

Hadoop Common: The common utilities that support the other Hadoop modules.
Hadoop Distributed File System (HDFS™): A distributed file system that provides high-throughput access to application data.
Hadoop YARN: A framework for job scheduling and cluster resource management.
Hadoop MapReduce: A YARN-based system for parallel processing of large data sets.

What’s Hive?

The Hive data warehouse software facilitates reading, writing, and managing large datasets residing in distributed storage using SQL. Structure can be projected onto data already in storage. A command line tool and JDBC driver are provided to connect users to Hive.

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[Ubuntu] Install Spark2.2.1 on Ubuntu 16.04

What is Spark?

Apache Spark is a fast and general-purpose cluster computing system. It provides high-level APIs in Java, Scala, Python and R, and an optimized engine that supports general execution graphs. It also supports a rich set of higher-level tools including Spark SQL for SQL and structured data processing, MLlib for machine learning, GraphX for graph processing, and Spark Streaming.

You can download Spark from here, or follow the below instructions to download and install Spark2.2.1.

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【Life】2017年學海無涯之線上課程教學評比：Coding/Programming Training篇

從2015年開始，我陸續使用過了不同的線上學習課程平台，像是Coursera, Udemy, Lynda.com, Codecademy, Udacity, Linux Academy, Cloud Academy。其中Linux Academy和Cloud Academy是只有IT DevOps訓練的平台，我會在別篇介紹，我在這裡介紹的是跟Coding & Programming相關的平台。此外在國外還算蠻有名的coding線上課程還有treehouse以及Code school，不過因為時間有限，這兩家的線上課程平台我並沒有特別去嘗試，有興趣的人可以找找國外的評價。

以下將會介紹

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[WP] How to Add SSL and HTTPS in WordPress?

SSL plays an important role in website, because in the last year Google announced that they will be using HTTPS and SSL as a ranking signal in their search results. This means that using HTTPS and SSL will help improve your site’s SEO.

Using an SSL certificate for your WordPress site means that your data, as well as your users’ data, remains safe from prying eyes. Since WordPress is a particularly large target for hackers due to its popularity and transparency, it’s important to take all the appropriate steps toward securing your site.

If you host a wordpress website by yourself, you may need to install SSL certificate on your website. I found a simple way to install SSL certificate through commands and the most important thing is this SSL certificate is free. Oh yes, you need to have the basic knowledge of SSH, Linux and Bash.

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[Android] How to solve the annoying toolbar stretching issue?

I’ve been developing an Android application recently, and I use Android v7 toolbar in my app instead of ActionBar. When I opened some views with EditText component, the toolbar stretched and occupied the whole view. It’s really annoying because users cannot see anything when they open this view unless they close the keyboard.

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[Java] 支付寶(alipay) 境內支付API介接與實作

最近因為公司業務拓展需求，需要將公司的平台導入支付寶(alipay)的API，讓買家可以直接使用支付寶付款。原本以為這是一個很簡單的任務，沒想到因為對支付寶API的不熟悉，來來回回折騰了將近兩週才將支付功能開發完成。

支付寶的支付接口分為境內支付以及國際支付兩種。所謂的境內支付指的是買家用人民幣付款，賣家用人民幣取款。而國際支付則是買家用人民幣付款，賣家可以用指定幣種取款。因為我的公司是紐西蘭公司，當然就是用紐幣取款了。

這兩種支付接口所使用的API以及傳入的參數是完全不一樣的，但因為一開始不知道兩種支付方式使用不同的API，一直在螞蟻金服開放平台上的官方文件糾結了很久。且網路上的資訊新舊交雜，導致程式都寫完了才發現螞蟻金服開放平台上演示的API只能用於境內支付。恍然大悟之後改去用國際支付的API，程式重新撰寫配置才將此支付功能完成。

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[AWS] How to tackle with the AWS Certified Developer Associate Level?

I attended the AWS Certified Developer – Associate exam on 4th March 2016, and eventually got this certification. I would like to tell you what the AWS Certified Developer – Associate is, and how I prepared for the examination.

What is AWS Certified Developer – Associate?

AWS Certified Developer – Associate is one of the AWS Certifications. AWS offers three categories of certification: Solutions Architect, SysOps Administrator and Developer. Each of these is currently available on an Associate or Professional level. Right now, there are five exams in total, since one exam covers both the Developer and SysOps Administrator on the Professional Level.

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How to find the longest possible quasi-constant subsequence of array?

This is my task2 challenge. I’ve tried to solve this question, but my result wasn’t good. Although there was no error after testing, I only got 33% score.😰

The summary of question shows as below:

I was given a non-empty unsorted array such as: A = [6, 10, 6, 9, 7, 8]. The amplitude of a subsequence of array A is the difference between the largest and the smallest element in this subsequence. The amplitude of the empty subsequence is assumed to be 0.

These are some of the subsequences of array A and their amplitudes:
[6, 6, 7] has amplitude 1;
[6, 10, 6, 9, 7, 8] has amplitude 4;
[6, 6, 7, 8] has amplitude 2.

If this subsequence of array is called quasi-constant, it means its amplitude does not exceed 1. In the example above, subsequence [6, 6, 7] is the longest possible quasi-constant subsequence of array A.

Now, you are expected to provide a method that takes in an array and returns the maximum number of quasi-constant subsequence of array. In above example, the function should return 3.

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